Intrinsic carrier multiplication in layered Bi 2 O 2 Se avalanche photodiodes with gain bandwidth product exceeding 1 GH
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Intrinsic carrier multiplication in layered Bi2O2Se avalanche photodiodes with gain bandwidth product exceeding 1 GHz Vinod K. Sangwan1, Joohoon Kang1,†, David Lam1, J. Tyler Gish1, Spencer A. Wells1, Jan Luxa2, James P. Male1, G. Jeffrey Snyder1, Zdeněk Sofer2, and Mark C. Hersam1,3,4 () 1
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic 3 Department of Chemistry, Northwestern University, Evanston, IL 60208, USA 4 Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL 60208, USA † Present address: School of Advanced Materials Science and Engineering, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 24 June 2020 / Revised: 26 July 2020 / Accepted: 14 August 2020
ABSTRACT Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities, strong light–matter interactions, and tunable optical absorption and emission. Here, metal-semiconductor-metal avalanche photodiodes (APDs) are fabricated from Bi2O2Se crystals, which consist of electrostatically bound [Bi2O2]2+ and [Se]2− layers. The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of ~ 400 kHz at a visible wavelength of 515.6 nm, ultimately resulting in a gain bandwidth product exceeding 1 GHz. Due to exceptionally low dark currents, Bi2O2Se APDs also yield high detectivities up to 4.6 × 1014 Jones. A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi2O2Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of ~ 44 meV, in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors. In this manner, layered Bi2O2Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.
KEYWORDS layered semiconductor, photodetector, high-frequency, Schottky diode, impact ionization
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Introduction
Layered semiconductors have attracted significant interest for both fundamental and applied optoelectronic research as a result of their excitonic physics, weak electrostatic screening, tunable optical absorption and emission, interlayer interactions, optically accessible topological states, and strong coupling to the environment and neighboring low-dimensional materials [1–7]. Among the many optoelectronic applications for layered semiconductors, photodetectors are particularly prominent [8]. Semiconductor photodetectors involve a two-step process where a photon is captured, and then the resulting electron–hole pair is separated to produce a photocurrent or photovoltage [1, 4, 9–12]. The
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